In the past, subsequent to drilling the wellbore, a liner is frequently installed prior to the onset of regular production. Typically, a procedure commonly known in the industry as gravel packing is performed. An assembly composed of a work string, a running tool assembly, a disconnect assembly, a packer assembly, and a liner assembly, is put together at the surface and lowered into the wellbore. If a gravel pack procedure is contemplated, a gravel pack crossover assembly is installed usually between the packer assembly and the liner assembly. In the past, after positioning the liner assembly at the desired location in the wellbore, the packer is set and the work string must be disconnected from the packer to be removed from the wellbore. Prior designs have involved disconnect assemblies that require rotation which allows a thread to disengage. Other mechanical connections that can be undone by rotation alone or in combination with a push or a pull have also been used in the past as the mode of disconnection between the disconnect assembly and the packer. Alternative designs have used pressure buildup which in turn creates a series of mechanical movements to facilitate disconnection between the disconnect assembly and the packer.
During routine operations with the liner systems described above, the entire assembly would be placed in the wellbore. The running tool would be actuated, thereby setting the packer. Thereafter, the disconnect assembly would be actuated to release the tubing string from the packer. At that time, if the particular operation called for it, a gravel pack procedure would be done. At the conclusion of a gravel pack procedure, the running tool assembly and the internal sections of the gravel pack crossover assembly are withdrawn, leaving the packer and liner assembly in the wellbore.
The prior systems for liner installation suffered from several drawbacks. One important drawback is a limited ability to rotate. The reason is that rotation could result in premature actuation of the disconnect assembly or setting the packer. Sometimes rotation is required, such as if the assembly is stuck in the wellbore. In those situations, experience has shown that many times the assembly can be unstuck if there is a capability to rotate. Previous designs have used shear pins to prevent premature actuation of the disconnect assembly. However, shear pins have a predetermined ability to resist shear forces up to the failure point. Sometimes forces larger than the capacity of the shear pins are required to liberate the assembly from a stuck position. As wellbores get more and more deviated or if they contain doglegs, the probability of sticking the assembly is increased. What has been lacking is a locking mechanism which ensures that the disconnect assembly will not be actuated upon the application of rotational force which may at times be necessary to further advance the assembly if it becomes stuck.
Another drawback of prior designs that actuate or disconnect hydraulically is that there are occasions, when running in the liner assembly, that the debris in the wellbore accumulates within the central flowpath or outside of the assembly. Experience has shown that to remove such accumulated debris within the central bore or on the outside of the assembly, pressure can be applied from the surface either through the annulus or through the central bore to circulate or reverse circulate this debris out of the wellbore. The debris needs to be removed so that subsequent procedures can take place. Unfortunately, if the assembly is hydraulically actuated, pressure buildup in trying to move accumulated debris, either within the central bore or in the annulus, can create sufficient forces to cause premature actuation of the running tool assembly and/or premature actuation of the disconnect assembly. Accordingly, what is needed is a tool and method of the present invention which prevents actuation, regardless of the amount of pressure buildup. This is done by constructing the apparatus in such a manner that deliberate steps must be taken at the surface in order for the pressure applied for debris removal to actuate either the running tool assembly, i.e., the packer, or the disconnect assembly adjacent the packer. One of several ways to do this is to provide a pressure-balanced tool assembly which accordingly cannot be actuated until a pressure-type plug device or other device is inserted into the assembly. Similarly, the disconnect assembly can be locked positively, using mechanical or hydraulic mechanisms which will not actuate on pressure buildup until several preliminary steps are deliberately taken. Without these preliminary steps, any application of pressure in the apparatus or outside of it will not actuate the setting assembly for the packer or the disconnect assembly adjacent the packer.
It should be noted that prior designs suffered from the problem of inadvertent actuation, regardless of whether the applied pressure was in the annulus or in the central flowpath. Some prior designs were set up to actuate on increasing annulus pressure.
Another drawback of the prior art has been that when using a gravel pack crossover assembly, circulation was not possible to the bottom of the liner assembly because the presence of the crossover assembly provided a path of least resistance immediately downhole from the packer assembly. The apparatus and method of the present invention provide a convertible gravel pack crossover assembly. The apparatus and method have been developed such that the necessary preliminary steps of defeating the various locks and setting the packer have incorporated a feature of converting the crossover sub into the crossover mode. Additional features have been added such that the mechanism which accomplishes this conversion from straight through to the crossover mode is physically retained in a sealing relationship against the circulation forces which act on it, which would in some instances tend to make the mechanism come away from the sealing surface. Accordingly, the apparatus and method have included a retaining feature for the sealing member which accomplishes the conversion to crossover flow. The apparatus and method of the present invention have the flexibility to allow circulation or reverse circulation to remove debris and changeover of a convertible gravel pack crossover assembly to permit deposition of the gravel outside the liner and a return flow through the crossover member out the annulus onto the surface.
One of the objects of this invention is to allow security for the operator to know that application of twisting forces or hydraulic pressure within the liner assembly or in the annulus outside will not inadvertently actuate the release mechanism or set the packer prematurely.